The exact mechanism of the pneumatization of the mastoid air cell system and the factors influencing the pneumatization are poorly understood. Both genetic as well as acquired factors have been implicated to influence this pneumatization process. Since pneumatization of the mastoid air cell system is considered an important prognostic factor in the outcome of reconstructive ear surgeries, a cohort study was carried out to assess the role of two important acquired factors i.e. duration of chronic otitis media and auditory tube functional status on the pneumatization of mastoid air cells. 50 individuals with unilateral chronic otitis media underwent assessment of their mastoid air cell system using planimetry and auditory tube functions using flourescein dye nasopharyngoscopy. The results were in accordance with the previous studies indicating a definite influence of chronic middle ear disease on the pneumatization process, although the duration of disease was not significant. In contrast to some of the previous studies, no influence of auditory tube functional status was found on the mastoid pneumatization